1) Field of the Invention
The present invention relates to an actuator for a vehicle, and more specifically, to an actuator for a door locking device of a four-wheel automobile.
2) Description of the Related Art
It is a common practice to provide a door locking device between an outside handle and a latch mechanism of a door provided in the chassis of the automobile. The latch mechanism normally includes a latch and a ratchet. When the automobile door is shut against the chassis, the latch engages in a striker provided on the chassis and the ratchet maintains this locked state.
The door locking device is locked and unlocked in a switchable manner by manual operation or electronic control. The manual operation involves using a key on the externally provided key cylinder or from within the chassis by pushing a locking button provided inside. The electronic control is performed, for example, by a so-called keyless entry with a remote controller.
The door locking device allows, when being in an unlocked condition, the door to be opened with the outside handle. Concretely, the ratchet releases its hold on the latch and the striker, thus enabling the door to be opened.
On the other hand, the door locking device does not allow, when being in a locked condition, the door to be opened with the outside handle. In other words, the ratchet maintains its hold on the latch and the striker.
Such a door locking mechanism includes an actuator disclosed in, for example, Japanese Utility Model Laid-Open Publication No. H5-52150, Japanese Utility Model No. 2513398, and Japanese Utility Model No. 2529569. FIG. 8 is a plan view of a conventional actuator. The actuator 100 includes a driving motor 110, a worm wheel 120, and an output lever 130.
The driving motor 110 is housed in a casing 1 and can turn both clockwise and counter-clockwise. The driving motor 110 is driven according to the electronic control, and has a driving shaft 1110 and a cylindrical worm 1120 mounted on the driving shaft 1110. The driving shaft 1110 and the worm 1120 turn in unison.
The worm wheel 120 is disc-shaped and is housed in the casing 1. The worm wheel 120 is rotatably supported by a supporting shaft 1210. The worm wheel 120 is engaged with the worm 1120 at a periphery of the worm wheel 120. Consequently, the worm wheel 120 is a rotor that turns in a normal direction or the opposite direction through the worm 1120 driven by the driving motor 110. The worm wheel 120 is illustrated in FIG. 8 as a rotor that turns clockwise or counter-clockwise. The worm wheel 120 is provided with a protrusion 200 that projects from the worm wheel 120.
The fan-shaped output lever 130 is swingably supported by an output shaft 1310 disposed on one side of the worm wheel 120. Precisely, the output lever 130 gradually broadens from a base 1320 of the output lever 130 towards a front end 1330 of the output lever 130. The base 1320 is shaft-supported and the front end 1330 swings freely. A groove 300 into which the protrusion 200 of the worm wheel 120 engages is provided on the front end 1330 that faces the worm wheel 120.
On the output shaft 1310 that shaft-supports the output lever 130, an output arm 1340 is shaft-supported. The output arm 1340 moves in unison with the output lever 130 through the output shaft 1310. The output arm 1340 is connected to a locking lever 140 which is a switching member. The locking lever 140 switches the door locking device between locked and unlocked condition by switching between a locked position and an unlocked position.
The actuator 100 electronically works in the manner described below when the door locking device is in a locked condition (that is, when the locking lever 140 is in the locked position). The driving motor 110 is driven to turn the worm wheel 120 in counter-clockwise direction. By this action the protrusion 200 of the worm wheel 120 engages in a first contact portion 300a of the groove 300 of the output lever 130. Once the worm wheel 120 and the output lever 130 are engaged in this fashion, further counter-clockwise rotation of the worm wheel 120 makes the protrusion 200 push the first contact portion 300a and makes the output lever 130 swing counter-clockwise. The output lever 130 switches the locking lever 140 to the unlocked position through the output arm 1340 which turns in unison with the output lever 130. Thus, the door locking device is in an unlocked condition. When the worm wheel 120 turns a complete 360 degrees and the protrusion 200 is back in its original position, the driving motor 110 ceases its operation.
The actuator 100 electronically works in the manner described below when the door locking device is in an unlocked condition (that is, when the locking lever 140 is in the unlocked position). The driving motor 110 is driven to turn the worm wheel 120 in clockwise direction. By this action the protrusion 200 of the worm wheel 120 engages in a second contact portion 300b of the groove 300 of the output lever 130. Once the worm wheel 120 and the output lever 130 are engaged in this fashion, further clockwise rotation of the worm wheel 120 makes the protrusion 200 push the second contact portion 300b and makes the output lever 130 swing clockwise. The output lever 130 switches the locking lever 140 to the locked position through the output arm 1340 which turns in unison with the output lever 130. Thus, the door locking device is in a locked condition. In this case too, when the worm wheel 120 turns a complete 360 degrees and the protrusion 200 is back in its original position, the driving motor ceases to be driven.
In the case of manual operation such as by insertion of key into the key cylinder or operation of the inside locking button, the locking lever 140 switches between the locked position and the unlocked position by a linking unit such as a link or a wire that links the locking lever 140 and the key cylinder or the inside locking button. The door locking device switches between locked and unlocked state in accordance with the locked or unlocked position of the locking lever 140. The actuator works in the following manner under such circumstances. The output lever 130 swings in unison with the output arm 1340 in accordance with the locked or unlocked position of the locking lever 140, while the protrusion 200 of the worm wheel 120 shifts in the groove 300. As a result, the output lever 130 stops at a predetermined position. Consequently, the switching of position of the locking lever by manual operation does not get transmitted to the worm wheel 120.
In the conventional actuator 100, the protrusion 200 provided on the worm wheel 120 moves in the groove 300 provided in the output lever 130 upon manual operation or electronic control of the door locking device. Consequently, it is necessary to have a fan-shaped output lever 130 which is sufficiently broad. In addition, it is necessary to make the sliding area of the output lever 130 to also cover the area outside of the perimeter of the worm wheel 120. Hence, the actuator cannot be made compact.